1. Field of the Invention
This invention relates to surgical fasteners, and more particularly to two part bioabsorbable fasteners comprising a fastener member and retainer piece.
2. Background of Related Art
Surgical fasteners, or staples, are commonly used in surgical procedures to allow a surgeon to fasten body tissue quickly without the need for time-consuming suturing. Such surgical fasteners may be applied by surgical staplers singly, in succession, or a number may be applied simultaneously.
Some types of surgical fasteners are two-part devices. That is, they are composed of a fastener, or staple, portion, which is generally a pronged U-shaped member, and a retainer portion, which has apertures into which the prongs are engaged and held. Such fasteners, once engaged, are not separable. Therefore, once inserted into body tissue they cannot be easily removed. For this reason, two part fasteners are made of bioabsorbable material, such as glycolide, lactide, or copolymers of glycolide and lactide.
One such fastener is disclosed in U.S. Pat. No. 4,060,089 ("Noiles"). A fastener strip with multiple barbed prongs is disclosed, along with a retainer strip with a plurality of longitudinally spaced openings for receiving the prongs.
U.S. Pat. No. 4,402,445 ("Green '445") discloses a two pronged fastener with a retainer piece.
U.S. Pat. No. 4,506,670 ("Crossley") discloses a two part surgical fastener wherein the retainer piece is held to a supporting member by a lug with a frangible member. The prongs of the fastener, upon entering the aperture of the retainer, breaks the frangible member and pushes out the lug, thereby releasing the retainer piece from the supporting member.
U.S. Pat. No. 4,513,746 ("Aranyi et al.") discloses a two piece fastener. The fastener portion has two prongs with outer channels. The retainer piece has extensions with apertures for receiving the prongs of the fastener, and longitudinally extending expansion slots.
U.S. Pat. No. 4,805,617 ("Bedi et al.") discloses a surgical fastener system comprising parallel rows of staples and receivers with the receivers connected to adjacent receivers by a plurality of linkages.
U.S. Pat. No. 4,534,352 ("Korthoff") discloses a surgical fastener member with an increased surface area to volume ratio for faster absorption.
U.S. Pat. No. 4,667,674 ("Korthoff et al.") discloses a surgical fastener having an extended base to reduce hemostatis.
U.S. Pat. No. 4,610,250 ("Green '250") discloses a two part surgical fastener. The fastener member has four prongs which mate with four openings in the retainer member. The two inner prongs are bent toward each other by camming surfaces in the corresponding openings in the retainer.
The following U.S. Design patents also illustrate fasteners: Des. 280,931; Des. 286,441; Des. 286,180; Des. 286,442 and Des. 280,932.
It is often desirable to place multiple rows of fasteners in stitching procedures. Two side by side rows of fasteners aligned end to end along the lengthwise direction of the fastener, for example, will exhibit greater holding power and hemostatis than one such row. To facilitate the placement of multiple rows it is desirable to have a staple which is as narrow as possible. However, the narrower one makes a fastener of any given length and shape, the weaker it is, because there is simply less structural material. For this reason, the structural features of surgical fasteners, which compensate for the lack of material by distributing or reducing stress, become increasingly important as the size is reduced. In particular, stresses are created when the fastener portion is locked into the retainer. This requires expansion of the aperture into which the barbed tip of the fastener prong enters. Although the material of construction, a bioabsorbable resin, has some degree of flexibility and resiliency, the elasticity sometimes can be insufficient to prevent breakage, especially if the retainer member is very narrow. What is needed, then, is a fastener which permits elastic expansion of the retainer piece along the lengthwise direction of the retainer.